1. Field of the Invention
The present invention relates generally to fibrous materials into which a lubricant has been compounded and more particularly to liner materials for magnetic record disk assemblies in which the porous, fibrous, low-friction anti-static liner material has a lubricant compounded into it.
2. Description of the Prior Art
Widely used in the computer industry is a data storage medium comprised of a circular disk of flexible material coated with magnetic particles enclosed within an envelope. These disks are known in the trade as "floppy disks." The envelope material is fabricated by bonding together a layer of porous, fibrous, low-friction, anti-static material and a layer of solid material. Both a method of constructing these envelopes and one type of porous, fibrous, low-friction, anti-static liner material are taught in U.S. Pat. No. 3,668,658 issued to Flores, et al.
Currently the porous, fibrous, low-friction, anti-static liner material is fabricated by bonding together a loose mass of synthetic fibers. Within the category of materials fabricated in the foregoing manner, there are two materials made from different compositions of fibers and formed into a whole mass in different ways, currently in wide use as floppy disk liner materials. The first kind includes a mixture of 70% to 80% rayon fibers with 30% to 20% polypropylene fibers. The polypropylene fibers have a lower softening temperature than the rayon fibers. Thus, a loose mixture of these fibers is normally bound into a cohesive layer by heating such a mass of fibers to the temperature at which the polypropylene fibers soften and adhere to each other and also the rayon fibers and then cooling the resultant material. The second type of material used for floppy disk liners includes almost entirely polyester fibers. This type of fiber is formed into a cohesive layer by applying a liquid binder solution containing, in addition to other substances, polyester molecules and a catalyst, to a mass of loose fibers. This coated mass of fibers is then further processed to polymerize certain components in the binder solution yielding a cohesive layer of bound fibers comprising approximately 93% polyester fibers and 7% polyester terpolymer binder. The polyester terpolymer binder is formed by the polymerization of the polyester molecules contained in the binder solution applied to the loose fiber mass.
The porous, fibrous, low-friction, anti-static materials when used as the liner of floppy disk envelopes are in intimate contact with the circular disk of flexible material coated with magnetic particles. These materials are employed to permit the disk to rotate easily within the envelope and, in addition, clean its recording surfaces of dust, wear products and airborne contaminants. During normal operation, the circular disk of flexible material coated with magnetic particles rotates constantly in frictional contact with the porous, fibrous, low-friction, anti-static liner material and, in addition, is in periodic frictional contact with one or more magnetic transducers used to write data to and read data from the circular disk of recording material. These frictional contacts to the circular disk of recording material both increase the amount of force required to rotate the circular disk of recording material within the envelope and, in addition, ultimately cause the coating of magnetic particles to wear away. For this reason, it is standard practice within the industry to compound lubricants into the coating containing magnetic particles applied to the circular disk of flexible material. However, it is generally difficult to maintain a stabilized concentration of this lubricant at the surface of the flexible disk of recording material over the life of the floppy disk assembly due to the wick action of conventional liner materials which act so as to continuously draw lubricant from the surface coating of the flexible disk.
Previous attempts to control the concentration of lubricant at the surface of the coating have consisted in dispersing a lubricant into the pores of the liner material formed when the constitutent fibers are bonded together. Such attempts to saturate the liner material with lubricant are exemplified by German Pat. No. 25 45 091 issued to Minnesota Mining and Manufacturing Co., U.S. Pat. No. 4,065,798 issued to Sugisaki, et al. and U.S. Pat. No. 4,106,067 issued to Masuyama, et al. The German Patent teaches the application of highly fluorine alkyl polyether to the liner material by pulling long strips of that material continually through a vat containing a mixture of the polyether dissolved in a solvent. Both the Sugisaki et al, and the Masuyama et al patents teach soaking the liner material with either a silicone resin, Teflon, a silicone oil, etc., in order to reduce the friction between the rotating disk of material and the envelope liner material.